In many mechanical applications, it is useful to sense the position of moving parts. For example, in many vehicular transmission systems that include forks it is necessary to sense the linear position of the fork to determine when a synchro is engaged or when the fork is in the neutral position. In dual clutch applications, it is also important to know the position of the fork when the torque is high since a smooth shift quality is desired.
In previous systems, various attempts have been made to accurately sense and determine the position of moving mechanical components. For example, in one previous approach, two linear position sensors and curved permanent magnets have been used in order to determine the position of the mechanical component between magnets. A vertical component (perpendicular to a back iron) of flux is plotted against position as the sensor is moved horizontally. An ideal plot of flux density is formed. The flux density is almost linear within a certain range but outside that range the flux density is non-linear and is usually avoided in position determination calculations. Non-linearity of the plot is typically not desirable because it complicates the relationship between the position to be measured and the physical quantity indicative of this position—it typically requires the use of a look-up table that accounts for the non-linearity and provides the desired relationship between actual position and the position indication quantity. Furthermore, the sensitivity of the system is reduced in cases where the non-linearity results in a reduction in the measured quantity for a given movement, thereby reducing the accuracy of the measurement due to the normal presence of noise in the measurement system.
Unfortunately, in these previous systems the maximum movement that can be accurately sensed is limited, in part, because the sensors could only determine distances between the magnets. Consequently, the movement of the part may be itself effectively limited because the accurate position of the moving mechanical part cannot be determined or sensed beyond a certain range. Even if the movement of the part is not limited, it was difficult or impossible to accurately determine the position of the moving part. In any case, these problems have led to performance degradation in previous systems, for example, in transmission systems. Performance degradation has then led to other problems such as user frustration and dissatisfaction with these previous approaches.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein.